Legal claims defining the scope of protection, as filed with the USPTO.
1. A secondary base station apparatus, comprising: a transmitter, which, in operation, transmits a change request of a secondary security key to a master base station when a value of a COUNT exceeds a threshold value, wherein the secondary security key is a security key for the secondary base station apparatus; a receiver, which, in operation, receives from the master base station an updated secondary security key, the updated secondary security key being derived at the master base station using an incremented freshness counter and a currently active security key of the master base station, without refreshing the current active security key of the master base station; and control circuitry, which, in operation, computes a new encryption key for communication with a mobile terminal using the updated secondary security key.
2. The secondary base station apparatus according to claim 1 , wherein the COUNT is composed of a packet data convergence protocol (PDCP) sequence number and a hyper frame number (HFN) that is shared between the base station and the mobile terminal.
3. The secondary base station apparatus according to claim 1 , wherein the control circuitry, in operation, re-establishes a communication link with the mobile terminal using the updated secondary security key.
4. The secondary base station apparatus according to claim 1 , wherein a RRCConnectionReconfiguration message is transmitted from the base station or the master base station to the mobile terminal after the master base station transmits the updated secondary security key.
5. The secondary base station apparatus according to claim 1 , wherein the freshness counter is a counter value for refresh of the secondary security key.
6. A communication method for a secondary base station apparatus, the communication method comprising: transmitting a change request of a secondary security key to a master base station when a value of a COUNT exceeds a threshold value, wherein the secondary security key is a security key for the secondary base station apparatus; receiving from the master base station an updated secondary security key, the updated secondary security key being derived at the master base station using an incremented freshness counter and a currently active security key of the master base station, without refreshing the currently active security key of the master base station; and computing a new encryption key for communication with a mobile terminal using the updated secondary security key.
7. The communication method according to claim 6 , wherein the COUNT is composed of a packet data convergence protocol (PDCP) sequence number and a hyper frame number (HFN) that is shared between the secondary base station and the mobile terminal.
8. The communication method according to claim 6 , comprising re-establishing a communication link with the mobile terminal using the updated secondary security key.
9. The communication method according to claim 6 , wherein a RRCConnectionReconfiguration message is transmitted from the secondary base station or the master base station to the mobile terminal after the master station transmits the updated secondary security key.
10. The communication method according to claim 6 , wherein the freshness counter is a counter value for refresh of the secondary security key.
Unknown
October 30, 2018
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